1. Field of the Invention
This present invention is directed to drilling wellbores in the earth, to systems for pumping drilling fluid (“mud”) for such operations, to pump modules for such systems, and methods of their use.
2. Description of Related Art
The prior art discloses a wide variety of drilling systems, apparatuses, and methods including, but not limited to, the disclosures in U.S. Pat. Nos. 6,944,547; 6,918,453; 6,802,378; 6,050,348; 5,465,799; 4,995,465; 4,854,397; and 3,658,138, all incorporated fully herein for all purposes. The prior art discloses a wide variety of drilling fluid pumps (“mud pumps”) used in drilling operations and pump systems; for example, and not by way of limitation, those pumps and systems disclosed in U.S. Pat. Nos. 6,257,354; 4,295,366; 4,527,959; 5,616,009; 4,242,057; 4,676,724; 5,823,093; 5,960,700; 5,059,101; 5,253,987; 6,718,955; and in U.S. application Ser. No. 10/833,921 filed Apr. 28, 2004 (all said U.S. references incorporated fully herein for all purposes).
By rotating a drill bit carried at an end of a drillstring wellbores are formed in the earth. Certain drillstrings include tubulars which may be drill pipe made of jointed sections or a continuous coiled tubing and a drilling assembly that has a drill bit at its bottom end. The drilling assembly is attached to the bottom end of the tubing or drillstring. In certain systems, to drill a wellbore, the drill bit is rotated by a downhole mud motor carried by the drilling assembly and/or by rotating the drill pipe (e.g. with a rotary system, power swivel, or with a top drive system). A drilling fluid, also referred to as “mud,” is pumped under pressure from a pit or container at the surface by a pumping system at the surface.
Drilling fluid or mud can serve a variety of purposes. It can provide downhole hydrostatic pressure that is greater than the formation pressure to control the pressure of fluid in the earth formation being drilled and to avoid blow outs. The mud drives a downhole drilling motor (when used) and it also provides lubrication to various elements of the drill string. Commonly used drilling fluids are either water-based or oil-based fluids. They can also contain a variety of additives which provide desired viscosity, lubricating characteristics, heat, anti-corrosion and other performance characteristics.
During drilling, the mud that is pumped downhole by the mud pump system is discharged at the bottom of the drill bit and returns to the surface via the annular space between the tubulars of the drillstring and the wellbore inside (also referred to as the “annulus”).
Certain prior, known mud pumps and mud pump systems have relatively complex and relatively heavy drive systems with typical connecting rods, eccentric shafts, and multiple rotating bearings, and many of these parts require constant lubrication. Certain prior “triplex” systems have a relatively large footprint.
Pending U.S. patent application Ser. No. 11/796,623 filed Apr. 27, 2007, co-owned with the present invention and incorporated fully herein for all purposes, discloses systems for pumping drilling fluid which include: a pump apparatus including a pumping section and a motor section; the pumping section having at least one pump, at least one inlet, and at least one outlet, and a main pinion shaft for operating the at least one pump; motor apparatus which is at least one AC motor; and the at least one AC motor directly connected to the main pinion shaft. In particular aspects, system for pumping drilling fluid are disclosed that include a pump apparatus including a pumping section and a motor section, the pumping section having at least one pump, at least one inlet, and at least one outlet, and a main pinion shaft for operating the at least one pump, motor apparatus comprising at least one AC motor, and the at least one AC motor directly connected to the main pinion shaft.
Pending U.S. patent application Ser. No. 11/414,163 filed Apr. 29, 2006, co-owned with the present invention and incorporated fully herein for all purposes, discloses drilling fluid pumping systems, also known as a mud pump systems, for pumping drilling fluid or mud used in wellbore operations in which a permanent magnet linear motor operates a pump apparatus to pump the fluid and the linear motor applies power directly. Such systems may have one, two-ten, or more mud pump apparatuses, each with a permanent magnet linear motor. In one aspect, a system is disclosed with pump apparatus with a pumping section and a motor section, the pumping section having an inlet and an outlet, the motor section having a shaft for reciprocating in and out of the pumping section to alternately suck fluid into the inlet and pump fluid out the outlet, and the motor being a permanent magnet linear motor for moving the shaft in a reciprocating motion, e.g., but not limited to, vertically or horizontally; and methods for using such a system.
FIG. 1 illustrates a prior art drilling fluid pump system S with internal pumping cylinders for pumping fluid through pump V with suction and discharge valves in a removable cartridge C. A service crane r with a pedestal P rotatably mounted on a bearing assembly B of the system S has a lift apparatus L movable on a beam E for lifting and moving system parts (e.g. pump modules, piston assemblies, roller forks). Motors T rotate pinion drives I to move a drive gear that in turn drives internal piston assemblies which drive the pumps V. In one particular aspect, the system S is a HEX 150 (Trademark) or a HEX 240 (Trademark) Pump System commercially available from National Oilwell Varco (owner of the present invention). The upper portion of the system S is like the upper portion of a system according to the present invention as shown in FIG. 3C.
The system S has a discharge ring D interconnected between and in communication with all the pump systems V. In some cases, such a discharge ring requires a relatively large space, has a relatively high weight and is relatively difficult to assemble. Also, due to internal flow direction changes, such a ring can shake during operation. In certain types of systems S, seats for the pump/valve system V are installed individually, e.g. press fit in place, and, therefore are destroyed when removed, e.g. as the result of an inspection of the inner valve. A cartridge C that has been removed is disassembled to inspect various parts, including the valve seats. In certain aspects in such prior systems expensive materials (e.g. S165M stainless steel) are used for parts and areas, e.g. standard known modules, which are subjected to high stress.